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A state in a d-dimensional Hilbert space can be simulated by a state defined in a different dimension withhigh fidelity. We assess how faithfully such an approximated state can perform quantum protocols using anexample of the sque...
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A state in a d-dimensional Hilbert space can be simulated by a state defined in a different dimension withhigh fidelity. We assess how faithfully such an approximated state can perform quantum protocols using anexample of the squeezed coherent superposition state, which was recently experimentally generated.
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Within the strong-field approximation, we study the time-resolved ionization process of a hydrogen atom in strong laser fields. At any time during the interaction between an atom and a laser field, the electron may instantaneously...
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Within the strong-field approximation, we study the time-resolved ionization process of a hydrogen atom in strong laser fields. At any time during the interaction between an atom and a laser field, the electron may instantaneously absorb all possible energies and build a wide momentum spectrum. As the interaction evolves in time, the coherent superposition of all previous instantaneous ionization events gradually filters out all other energy components except the part with an energy nω ? I_p, where I_p is the ionization potential, ω is the photon energy, and n is a positive integer. The establishment of the electron energy spectra in above-threshold ionization, rescattering, and streaking can all be directly viewed by tracking the time-dependent momentum spectra.
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Quantum resources, such as discord and entanglement, are crucial in quantum information processing. In this paper, quantum resources are studied from the aspect of quantum state superposition. We define the local superposition (LS...
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Quantum resources, such as discord and entanglement, are crucial in quantum information processing. In this paper, quantum resources are studied from the aspect of quantum state superposition. We define the local superposition (LS) as the superposition between basis of single part, and nonlocal superposition (NLS) as the superposition between product basis of multiple parts. For quantum resource with nonzero LS, quantum operation must be introduced to prepare it, and for quantum resource with nonzero NLS, nonlocal quantum operation must be introduced to prepare it. We prove that LS vanishes if and only if the state is classical and NLS vanishes if and only if the state is separable. From this superposition aspect, quantum resources are categorized as superpositions existing in different parts. These results are helpful to study quantum resources from a unified frame.
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Quantum states are constructed as a superposition of a few coherent states on a truncated von Neumann lattice. It is shown that the reconstruction is robust, in the sense that random noise in the coefficients affects the construct...
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Quantum states are constructed as a superposition of a few coherent states on a truncated von Neumann lattice. It is shown that the reconstruction is robust, in the sense that random noise in the coefficients affects the constructed state weakly. Numerical results for squeezed states and number eigenstates demonstrate that the technique is very accurate. [References: 11]
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We argue that the deeper nature of computation is to reduce the statistical obstruction against prediction. From this, we derive an explicit measure of computation for general, artificial as well as natural, systems (electronic ci...
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We argue that the deeper nature of computation is to reduce the statistical obstruction against prediction. From this, we derive an explicit measure of computation for general, artificial as well as natural, systems (electronic circuits, neurons, mechanical devices, etc.). The applicability and usefulness of this concept is demonstated using well-studied families of dynamical systems, as well as experimental time series from cortical neurons. (C) 2004 American Institute of Physics.
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We witness experimentally the presence of macroscopic coherence in Gaussian quantum states using a recently proposed criterion [E. G. Cavalcanti and M. D. Reid, Phys. Rev. Lett. 97 170405 (2006)]. The macroscopic coherence stems f...
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We witness experimentally the presence of macroscopic coherence in Gaussian quantum states using a recently proposed criterion [E. G. Cavalcanti and M. D. Reid, Phys. Rev. Lett. 97 170405 (2006)]. The macroscopic coherence stems from interference between macroscopically distinct states in phase space, and we prove experimentally that a coherent state contains these features with a distance in phase space of 0.51 +/- 0.02 shot noise units. This is surprising because coherent states are generally considered being at the border between classical and quantum states, not yet displaying any nonclassical effect. For squeezed and entangled states the effect may be larger but depends critically on the state purity.
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The overlap of two wave pulses that are moving in opposite directions along the same line in a linear, nondissipative and nondispersive medium is used to discuss the compatibility of wave superposition and of energy-momentum conse...
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The overlap of two wave pulses that are moving in opposite directions along the same line in a linear, nondissipative and nondispersive medium is used to discuss the compatibility of wave superposition and of energy-momentum conservation. What happens to the energy and to the momentum when the pulses overlap in such a situation is examined. The treatment is applicable to electromagnetic waves or to small-amplitude linear mechanical waves on an ideal string. It is argued that introductory-to-intermediate textbooks and the pedagogical literature have neglected these questions, particularly the one relating to the conservation of linear momentum. (C) 2003 American Association of Physics Teachers. [References: 17]
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We propose a measure for the "size" of a quantum superposition of two many-body states with (supposedly)macroscopically distinct properties by counting how many single-particle operations are needed to map onestate onto the other....
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We propose a measure for the "size" of a quantum superposition of two many-body states with (supposedly)macroscopically distinct properties by counting how many single-particle operations are needed to map onestate onto the other. This definition gives sensible results for simple, analytically tractable cases and is consis-tent with a previous definition restricted to Greenberger-Horne-Zeilinger-like states. We apply our measure tothe experimentally relevant, nontrivial example of a superconducting three-junction flux qubit put into asuperposition of left- and right-circulating supercurrent states, and we find the size of this superposition to besurprisingly small.
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Most authors in room acoustics qualify the mirror source method (MS-method) as the only exact method to evaluate sound fields in auditoria. But evidently nobody applies it. The reason for this discrepancy is the abundantly high nu...
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Most authors in room acoustics qualify the mirror source method (MS-method) as the only exact method to evaluate sound fields in auditoria. But evidently nobody applies it. The reason for this discrepancy is the abundantly high numbers of needed mirror sources which are reported in the literature, although such estimations of needed numbers of mirror sources mostly are used for the justification of more or less heuristic modifications of the MS-method. The present, intentionally tutorial article accentuates the analytical foundations of the MS-method whereby the number of needed mirror sources is reduced already. Further, the task of field evaluation in three-dimensional spaces is reduced to a sequence of tasks in two-dimensional room edges. This not only allows the use of easier geometrical computations in two dimensions, but also the sound field in corner areas can be represented by a single (directional) source sitting on the corner line, so that only this "corner source" must be mirror-reflected in the further process. This procedure gives a drastic reduction of the number of needed equivalent sources. Finally, the traditional MS-method is not applicable in rooms with convex corners (the angle between the corner flanks, measured on the room side, exceeds 180degrees). In such cases, the MS-method is combined below with the second principle of superposition (PSP). It reduces the scattering task at convex corners to two sub-tasks between one flank and the median plane of the room wedge, i.e., always in concave corner areas where the MS-method can be applied. (C) 2002 Elsevier Science Ltd. All rights reserved. [References: 16]
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